Radiopharmaceutical formulations

ABSTRACT

A method is described for inhibiting the degradation of a diagnostic or radiotherapeutic radiopharmaceutical, especially radiolabeled compounds containing reducible moieties, by including oxidants either as a part of the composition for the preparation of such radiopharmaceuticals, or by adding an oxidant to such compositions immediately after the preparation of such radiopharmaceuticals.

FIELD OF THE INVENTION

The present invention relates to radiopharmaceutical compositions,methods for inhibiting the degradation of a diagnostic orradiothierapeutic radiopharmaceutical, and kits containing suchradiopharmaceuticals.

BACKGROUND OF THE INVENTION

Because of the short half-life of the radionuclide, radiopharmaceuticalsare generally prepared within hours of their administration, usingformulations for the preparation of the product that contain allreagents except for the radionuclide.

Radiopharmaceuticals based, for example, on the radionuclides ^(99m)Tc,⁵¹Cr, ⁶⁷Cu, ⁹⁷Ru, ¹⁸⁸Re, ¹⁸⁶Re, and ¹⁹⁹Au, can be prepared by reactionwith a reducing agent, such as a stannous source, to reduce the metal inan oxidized state to a reduced state that can coordinate with thedesired ligand. Useful reducing agents include, for example, stannouschloride, stannous pyrophosphate, stannous fluoride, stannous tartrate,stannous glucoheptonate, stannous DTPA, sodium or other salts ofborohydride, sodium dithionite, Cu(l) salts, formamidine sulphinic acidand the like.

Radiopharmaceuticals are usually prepared from a freeze-dried formulatedproduct in “kit” form. These kits typically contain all of the reagentsrequired for the preparation of the radioactive product except theradionuclide and diluenis such as saline. For example, the kit containsa complexing ligand able to coordinate to a radionuclide, such astechnetium, and a reducing agent, such as a stannous source, that canreduce the radionuclide to a reduced state that can coordinate to theligating molecule (for example, technetium is reduced from ^(99m)TcO₄ ⁻,the form of technetium that is widely available, to a state that cancoordinate with the desired ligand).

Examples of complexing ligands are those found in the following ^(99m)Tckit radiopharmaceuticals: Kits for the preparation of^(99m)Tc-bis(bis(2-ethyloxyethyl)phosphino)ethane (^(99m)Tc-Myoview,^(99m)Tc-Tetrofosmin).^(99m)Tc-trans(1,2-bis(dehydro-2,2,5,5,-tetramethyl-3-furanone-4-methylene-amino)ethane)-tris(3-methoxy-1-propyl)phosphine(^(99m)Tc-Technescan Q12. ^(99m)Tc-Furifosmin).^(99m)Tc-methoxyisobutylisonitrile (^(99m)Tc-M1B1).^(99m)Tc-1,1-ethylenecysteine diethylester dimer (^(99m)Tc-ECD).^(99m)Tc-d,1-hexamethylene propyleneamine oxime (^(99m)Tc-HMPAO).^(99m)Tc-diethylenetriaminepentaacetic acid (^(99m)-Tc-DTPA),^(99m)Tc-ethylene hepatobiliary iminodiacetic acid (^(99m)Tc-EHIDA),^(99m)Tc-1,1-ethylenecysteine dimer (^(99m)Tc-EC),^(99m)Tc-mercaptoacetylglycylglycylglycine (^(99m)Tc-MAG3),^(99m)Tc-dimercaptosuccinic acid (^(99m)Tc-DMSA), and ^(99m)Tc-methylenediphosphonate (^(99m)Tc-MDP).

Alternatively, radiopharmaceuticals may be formed by reacting anappropriate complexing agent with a radionuclide, such as technetium orrhenium, that has been pre-reduced in the presence of a weaklycoordinating labile ligand known as a “transfer” or “exchange” ligand.This process is known as ligand exchange and is well known to thoseskilled in the art.

The useful life of a reconstituted radiopharmaceutical product isdictated by the radiochemical purity (RCP) of this product (i.e. thepercentage of the radiolabeled product that is the compound ofinterest). A common problem in this area is that the desiredradiolabeled compound often begins to decompose immediately after theproduct is made. If this rate of decomposition is fast, an unacceptablelevel of degradation is reached before the radiolabeled product can beadministered to the patient to provide beneficial effect. In general,after the RCP drops below 90%, the compound can no longer be used.Additives that can increase the post-reconstitution shelf-life of theproduct are therefore important. this is especially important when theradiolabeling is performed at a central radiolabeling facility, and theradiolabeled compound is then shipped to the site of patientadministration.

Typically, the stabilizers that are added are antioxidants. The purposeof these stabilizers is to prevent any stannous ion [Sn(2+)] thatremains in the vial after the formation of the desired complex frombeing oxidized to Sn(4+) and to keep the complex of interest from beingoxidized back to the starting material (TcO₄ ⁻). The use ofantioxidants, such as gentisic acid and ascorbic acid, as stabilizersfor diagnostic radiopharmaceuticals based on ^(99m)Tc has been describedin various references, including: EP-A-46067; Tofe et al, Radiopharm. 2,Proc. Int. Symp., 2nd (1979); Solanki et al, C. B. Nucl. Med. Commun.(1994), 15(9). 718-22; Clcyhens et al. Lab. Nucl. Med. Radiopharm.,Nuklearmedizin, Suppl. (1991), 27 133-5: EP-A-313712; DE 3323375; Res.Discl. (1989), 305 666. In general, the goal of the use of thesestabilizers is to prevent oxidation of the product and maintain stannouslevels for as long as possible.

However, in some cases, excess antioxidant or reducing agent in the vialmay have a deleterious effect on the long-term post reconstitutionstability of radiopharmaceutical products. For example, compounds whichcontain reducible functional groups such as aromatic nitro groups,nitroimidazoles, and disulfide bonds that can react with the stannousion may be reduced to forms that are no longer biologically active (inmolecules that target biological targets), or the central metal can bereduced to lower oxidation states that do not have the same desirablecharacteristics as the desired product. Previous attempts to stabilizeradiopharmaceutical complexes have used oxidizing agents, but havefailed to provide a radiopharmaceutical with greater than 90%radiochemical purity after even thirty minutes. In addition, theoxidizing agents used in these earlier attempts cannot be added prior tocomplex formation, and/or cannot be lyophilized for use in kits.

Thus, there is a need for stabilizers that can inhibit degradation of adiagnostic or radiotherapeutic radiopharmaceutical by further reductionof either the ligand molecule that is coordinated to the radioactivemetal or of the central metal itself. In particular, there is a need forradiopharmaceuticals with radiochemical purity of greater than 90% forup to six hours after reconstitution. There is also a need in the artfor radiopharmaceutical preparations with fewer impurities. Moreover,there is a need for radiopharmaceutical preparations containing anoxidizing agent that may be lyophilized for use in kits. In addition,there is a need for radiopharmaceutical preparations which allowaddition of an oxidizing agent prior to complex formation. Suchpreparations would permit inclusion of the oxidizing agent in the samevial as the complexing ligand, thereby decreasing manufacturing cost andincreasing ease of use.

SUMMARY OF THE INVENTION

The present invention provides compounds that stabilizeradiopharmaceutical formulations by inhibiting degradation of theformulations due to further reduction of reducible moieties on thechelating or complexing ligand, or further reduction of the centralradioactive metal ion. By adding the appropriate oxidant to theformulation of a radiopharmaceutical for diagnostic or therapeuticpurposes, this degradation can be prevented.

The present invention can be applied to a wide variety ofradiopharmaceuticals that are formed by reduction of a radioactive metalusing an excess of reducing agent in the presence of a chelating or acomplexing ligand (such as monodentate and polydentate ligands known inthe art), and wherein further reduction of either

-   -   a. the central radioactive metal ion, or    -   b. a reducible moiety on the chelating or complexing ligand can        take place after the formation of the complex. The oxidants of        the present invention can be used to prevent such further        reduction.

In the first case, reaction with excess reductant after the desiredcompound has formed may cause the central metal to be reduced from thedesired oxidation state (e.g. Tc or Re(V)) to a lower one (e.g. Tc or Re(IV or III)).

In the second case, excess reductant present after the desired compoundhas formed may cause a readily reducible group on the chelating orcomplexing ligand to be further reduced.

The present invention also provides stabilized formulations ofradiopharmaceuticals containing an oxidant of the invention in order toinhibit such degradation. In one aspect, the invention provides apharmaceutical composition which includes a radiopharmaceutical and anoxidant, wherein the radiopharmaceutical has a radiochemical purity ofgreater than about 90% at about six hours after reconstitution.Preferably, the radiopharmaceutical has a radiochemical purity ofgreater than about 92% at about six hours after reconstitution, mostpreferably, greater than about 95% at about six hours afterreconstitution. In some embodiments of the invention, the oxidant is aquinone, such as benzoquinone. In preferred embodiments, the oxidant isan ubiquinone, most preferably coenzyme Q₀.

The present invention also provides single or multi-dose kits forpreparing a radiopharmaceutical composition, wherein the kits include anoxidant of the invention. In a preferred embodiment, the kit includes avial containing both an oxidant and a complexing ligand. In anotherpreferred embodiment, the kit includes a lyophilized composition, whichincludes a predetermined amount of a complexing ligand and predeterminedamount of an oxidant. Radiopharmaceuticals prepared from kits of theinvention have a radiochemical purity of greater than about 90% at aboutsix hours after reconstitution, more preferably, greater than about 92%at about six hours after reconstitution, and most preferably, greaterthan about 95% at about six hours after reconstitution. In otherembodiments, the kits of the invention include a reducing agent. In someembodiments of the invention, the oxidant included in the kit is aquinone, such as benzoquinone. In preferred embodiments, the oxidant isan ubiquinone, most preferably coenzyme Q₀.

The present invention also provides methods of makingradiopharmaceutical with a radiochemical purity of greater than about90% at about six hours after reconstitution, more preferably, greaterthan about 92% at about six hours after reconstitution, and mostpreferably, greater than about 95% at about six hours afterreconstitution. In one aspect, the invention provides a method of makinga radiopharmaceutical which includes the steps of: a) contacting acomplexing ligand with a radionuclide to form a complex; and b)contacting the complexing agent with an oxidant, wherein theradiopharmaceutical has a radiochemical purity of greater than about 90%at about six hours after reconstitution. In one preferred embodiment,step b) is performed before step a). In another preferred embodiment,steps a) and b) are performed simultaneously. In some embodiments of theinvention, the oxidant used in the method is a quinone, such asbenzoquinone. In preferred embodiments, the oxidant used in the methodis an ubiquinone, most preferably coenzyme Q₀.

Among those benefits and improvements that have been disclosed, otherobjects and advantages of this invention will become apparent from thefollowing description. The tables and charts constitute a part of thisspecification and include exemplary embodiments of the present inventionand illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the HPLC chromatogram of a radiopharmaceutical preparation inthe absence of an oxidant. HPLC was performed approximately six hoursafter reconstitution.

FIG. 2 is the HPLC chromatogram of a radiopharmaceutical preparation inthe presence of p-aminobenzoic acid. HPLC was performed approximatelysix hours after reconstitution.

FIG. 3 is the HPLC chromatogram of a radiopharmaceutical preparation inthe presence of an oxidant of the invention. HPLC was performedapproximately six hours after reconstitution.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousforms. The figures are not necessarily to scale, and some features maybe exaggerated to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a basis for the claims and asa representative basis for teaching one skilled in the art to variouslyemploy the present invention.

The present invention provides compounds that stabilizeradiopharmaceutical formulations by inhibiting degradation of theformulations due to further reduction of reducible moieties on thechelating or complexing ligand or further reduction of the centralradioactive metal ion. In one embodiment, the radiochemical purity (RCP)in a radiopharmaceutical product is greater than about 90% for at leastsix hours (time of utilization of most of ^(99m)Tcradiopharmaceuticals), and the product includes as few impurities aspossible. As a result, the radiopharmaceutical formulations containingthe stabilizing compounds of the invention show improved stability andreduced levels of impurities, permitting RCPs of greater than 90% aftersix hours.

As used herein, “radiochemical purity” or “RCP” is determined asfollows:

-   -   RCP=(100−M)(C/100) where    -   M=% of radiocolloid, as determined by paper chromatography    -   C=% radiopharmaceutical, as determined by HPLC

In another aspect, the invention provides a radiopharmaceutical having areduced impurity content. Preferably, radiopharmaceutical compositionsof the invention have an impurity content of less than about 6%, morepreferably less than about 4%, and most preferably less than about 2%,For example, in FIG. 1, FIG. 2, and FIG. 3. “hydrophilic impurities” areidentified to the left of the radiopharmaceutical peak, and “hydrophobicimpurities” are identified to the right of the radiopharmaceutical peak,in addition to the impurities contributed by the starting materials.

The present invention preferably uses a quinone to prevent furtherreduction of the radiopharmaceutical. As used herein, the term “quinone”refers to both unsubstituted and substituted quinones of the followinggeneral structure:

where R₁, R₂, R₃, and R₄ are independently selected from hydrogen,hydroxyl, halogen, lower alkyl (including branched, straight chain,substituted and unsubstituted alkyl), alkoxy, aryl (includingsubstituted and unsubstituted aryl), heteroaryl, NO₂ and

where n is an integer from 0 to 12; or where R₁ and R₂ taken togetherform a ring (either substituted or unsubstituted), and R₃ and R₄ are asdefined above. For example, R₁ and R₂ taken together may form a fusedring comprising five to seven carbon atoms, preferably comprising sixcarbon atoms. The fused ring may be saturated, unsaturated, or aromatic.Preferably, the fused ring is an aromatic ring. For example, when R₁ andR₂ taken together form a benzene ring, and R₃ and R₄ are each hydrogen,the oxidant of the invention may be one of the following:

A preferred class of quinones used in the present invention areubiquinones, or coenzymes Q, of the following structure:

where n is an integer from 0 to 12.

Preferred oxidants include benzoquinone, CAS Registry No. 106-51-4, andcoenzyme Q₀, with coenzyme Q₀ being the most preferred. Benzoquinone (or“2,5-cyclohexadiene-1,4-dione” or “p-quinone” or “1,4-benzoquinone” or1,4-cyclohexadienedione”) and coenzyme Q₀ have the following chemicalstructures:

Preferred oxidants of the present invention may be added either prior tocomplexation or after formation of the radiopharmaceutical. According tothe invention, an oxidant may be used alone or in combination with oneor more other oxidants. An artisan skilled in the radiopharmaceuticalfield will be able to determine by routine experimentation, followingthe teachings herein, the optimal type(s) of oxidant, the amount, etc.,used for a given application, e.g., for a given complexing ligand. Forexample, the oxidant should be present in sufficient concentration tooxidize any reductant that remains after complexation. As taught herein,where the reductant is stannous, the ratio of stannous to oxidant mayrange from about 1:0.39 to about 1:25.

Furthermore, certain oxidants (such as iodine) sublime, and thus are notuseful in freeze dried or lyophilized formulations, which are mostcommercially useful due to, e.g., longer shelf life. Oxidants thatsublime are thus not useful for manufacturing kits for commercial usebecause of the reduced shelf life of these formulations. In particular,non-lyophilized formulations may undergo hydrolysis, and are accordinglyless desirable than lyophilized formulations.

The present invention can be applied to a wide variety ofradiopharmaceuticals that are formed by reduction of a radioactive metalusing an excess of reducing agent in the presence of a chelating orcomplexing ligand, and wherein further reduction of either:

-   -   a. the central radioactive metal ion, or    -   b. a reducible moiety on the chelating or complexing ligand can        take place after the formation of the complex.

Radiopharmaceuticals useful in the invention include those that can beprepared by a reaction with a reducing agent able to reduce the metal inan oxidized state to a reduced state that can coordinate with thedesired ligand, such as a stannous source, sodium borohydride, Cu(I)salts, formamidine sulphinic acid and the like. Thus,radiopharmaceuticals based, for example, on the following radionuclides^(99m)Tc (and other isotopes of Tc), ⁵¹Cr, ⁶⁷Cu, ⁹⁷Ru, ¹⁸⁸Re, ¹⁸⁶Re, and¹⁹⁹Au are useful in the invention. ¹⁸⁸Re, ¹⁸⁶Re and ^(99m)Tc isotopesare preferred.

The oxidants of the invention may be used to stabilizeradiopharmaceutical formulations in which reaction with excess reductantafter the desired compound has formed would otherwise cause the centralmetal to be reduced from the desired oxidation state (e.g. Tc or Re(V))to a lower one (e.g. Tc or Re (IV or III)). For example, oxidants of theinvention may be used to prevent reduction of Tc(V) (in for exampleTc-MAG3 or Tc-phosphine based compounds) to a lower oxidation state(such as Tc(IV) in the case of Tc-MAG3 or Tc(III) or Tc(I) in the caseof Tc-phosphine compounds).

Additionally, the present invention is useful to stabilizeradiopharmaceutical formulations in which excess reductant present afterthe desired compound has been formed would otherwise cause a readilyreducible group on the chelating or complexing ligand to be furtherreduced.

Thus the oxidants of the invention may be used with radiopharmaceuticalscontaining a wide variety of chelating or complexing ligands to inhibitdegradation due to further reduction of reducible moieties on suchligands. Many ligands that bind to radionuclide metals are tetradentateand contain a combination of four nitrogen and/or sulfur metalcoordinating atoms (i.e. N4, N3S, N2S2 and the like). For example, N4chelators are described in U.S. Pat. Nos. 6,093,382; 5,608,110;5,665,329, 5,656,254; and 5,688,487. Certain N₃S chelators are describedin PCT/CA94/00395 and in PCT/CA94/00479. The invention may apply toderivatives of the complexing ligandmercapto-acetyl-acetyl-glycyl-glycine (MAG3), which contains an N3S, andto N2S2 systems such as MAMA, DADS, CODADS and the like. These ligandsystems and a variety of others are described in Liu and Edwards. ChemRev. 1999, 99, 2235-2268 and references therein. The disclosures of eachof the foregoing patents, applications and references are incorporatedby reference herein, in their entirety.

This invention is also potentially applicable to complexes containingligand atoms which are not donated to the metal in a tetradentate array.These include the boronic acid adducts of technetium and rheniumdioximes, such as are described in U.S. Pat. Nos. 5,183,653: 5,387,409;and 5,118,797, the disclosures of which are incorporated by referenceherein, in their entirety.

The possible reducible groups present in the ligand molecule mayinclude, for example: aldehydes, ketones, α-substituted lactones,conjugated ketones, α-substituted esters, sugar lactones, cyclicanhydrides, N-alkylphthalimides, imines and iminium salts, aromaticnitro groups, nitrosamines, quinones, sulfenyl chlorides,1,2-diketoethylenes, naphthoquinones, o-alkyl dioxaimines, catechols,and ortho phenylenediamines.

Such reducible groups may also be heterocyclic groups less resistant tothe reduction conditions due to the presence of an electron withdrawingsubstituent, like a nitro group. This may occur, for example, in imagingagents that bear a nitroimidazole group on the complexing ligand. Thenitroimidazole moiety in these agents is used to target the radiolabeledcompound to hypoxic tissue (see for example H. J. Machulla, Imaging ofHypoxia, Vol.33, Developments in Nuclear Medicine, Kluver Publ., 1999).Further reduction of this targeting group may remove such targetingability.

In a second example, the reaction of excess reducing agent with adisulfide bond in a protein or in a ligand that bears a cyclic peptidemay cause this disulfide bond to be reduced to yield two free thiols,opening the cyclic ring and potentially abolishing the ability of suchprotein or cyclic peptide to bind to its target. See for example Thakuret al, J. Labelled Compounds and Radiopharmaceuticals 1993, Vol. 32,p.365-367.

The invention is of particular utility when there is an imidazole moietypresent on the ligand molecule, and more particularly when a nitro groupis present in the cycle, as described in U.S. Pat. No. 5,665.329, Su,Zi-Fen et al, Bioconjugate Chem. (2000), 11(5), 652-663: WO-A-0043004;Zhang, Xiuguo et al., Bioconjugate Chem. (2000), 11(3), 401-407. Thedisclosures of each of the foregoing patents, applications andreferences are incorporated by reference herein, in their entirety.

It should be understood that the foregoing ligand systems are providedonly as examples, and that modifications or alternatives that areequivalent to it within the spirit and scope of the invention areenvisaged.

In a preferred embodiment of the present invention, oxidants of theinvention are added to radiopharmaceutical formulations having acompound of Formula I, a ^(99m)Tc(V)-diamine dioxime complex thatcontains a 2-nitroimidazole substituent:

This compound localizes preferentially in hypoxic tissue and haspotential applications in pathologies characterized by low oxygencontent such as identification of viable versus necrotic tissuefollowing myocardial infarction or stroke and the detection of hypoxictumors. The nitroimidazole group is responsible for the hypoxic tropismof the compound of Formula I. Nitroimidazoles are normally reduced inall viable cells, but in the absence of an adequate supply of oxygenthey undergo further reduction to more reactive products that bind tocell components (see, for example, Edwards DI; Nitroimidazolesdrugs-action and resistance mechanism. I. Mechanism of action, J.Antimicrob. Chemother. 1993, 31, 9-20).

The proposed multi-step reduction pathway for nitroimidazoles in thecell is as follows:

The oxidants of the invention may be used to improve the stability offormulations having a compound of Formula I. Indeed, as shown in moredetail in Example 2 below, use of an oxidant of the present inventionwith formulations having a compound of Formula I, whether added beforeor after complexation, stabilized the radiopharmaceutical preparation,eliminating a lipophilic impurity caused by reduction of thenitroimidazole group and permitting RCPs of well over 90% at six hours.Use of benzoquinone, CAS Registry No. 106-51-4, and coenenzyme Q₀ asstabilizers in formulations having a compound of Formula I gave RCPsranging from 94-96% at six hours.

The present invention may also provide stabilized formulations ofradiopharmaceuticals containing an oxidant of the invention as well asthe appropriate and usual additives such as buffers, bulking agents,etc. In another embodiment, the present invention may also includesingle and/or multi-dose kits for preparing formulations ofradiopharmaceuticals containing a stabilizing oxidant of the invention.Several potential kit formulations are envisioned. For example, thecomplexing ligand and oxidant may be present in one vial while thestannous or other reducing source may be present in a second vial. Inanother example, the kit formulation may include the complexing ligandin one vial, the stannous source in a second vial and the oxidant in athird vial. In yet another example, the kit may include a transfer (ortrans-chelating) ligand and stannous or other reducing agent in thefirst vial and the complexing ligand and oxidant in the second vial.Similarly, in an additional kit formulation, a transfer ligand andstannous or other reducing agent are present in one vial, the complexingligand is in a second vial and the oxidant is present in a third vial.In a further embodiment, the kit formulations may include the usualadditives and bulking agents known to those skilled in the art. Methodsof reconstituting the kits with radioisotopes are well known to thoseskilled in the art.

Kits of the present invention comprise one or more vials containing thesterile formulation of a predetermined amount of a complexing ligand, anoxidant and optionally other components such as reducing agents,transfer ligands, buffers, lyophilization aids or bulking agents,stabilization aids, solubilization aids and bacteriostats. The inclusionof one or more optional components in the formulation will frequentlyimprove the ease of synthesis of the radiopharmaceutical by thepracticing end user, the ease of manufacturing the kit, the shelf-lifeof the kit, or the stability and shelf-life of the radiopharmaceutical.The improvement achieved by the inclusion of an optional component inthe formulation must be weighed against the added complexity of theformulation and added cost to manufacture the kit. The one or more vialsthat contain all or part of the formulation can independently be in theform of a sterile solution or a lyophilized solid.

Buffers useful in the preparation of radiopharmaceuticals and indiagnostic kits useful for the preparation of the radiopharmaceuticalsinclude but are not limited to phosphate, citrate, sulfosalicylate, andacetate. A more complete list can be found in the United StatesPharmacopeia.

Lyophilization aids or bulking agents useful in the preparation ofdiagnostic kits useful for the preparation of radiopharmaceuticals areknown in the art and include lactose, sodium chloride, maltose, sucrose,PEG 8000, cyclodextrins, such as hydroxypropyl-γ-cyclodextrin (HP-γ-CD),dextran, Ficoll, and polyvinylpyrrolidine (PVP). Of these, sodiumchloride, maltose, sucrose, PEG 8000, HP-γ-CD, and dextran are preferredbulking agents for use with the invention, with maltose, sucrose. andHP-γ-CD being the most preferred.

Stabilization aids useful in the preparation of radiopharmaceuticals andin diagnostic kits useful for the preparation of theradiopharmaceuticals include but are not limited to ascorbic acid,para-aminobenzoic acid (PABA), cysteine, monothioglycerol, sodiumbisulfite, sodium metabisulfite, gentisic acid and inositol.

Solubilization aids useful in the preparation of radiopharmaceuticalsand in diagnostic kits useful for the preparation of theradiopharmaceuticals include but are not limited to ethanol, glycerin,polyethylene glycol, propylene glycol, polyoxyethylene sorbitanmonooleate, sorbitan monooloeate, polysorbates,poly(oxyethylene)poly(oxypropylene)poly(oxyethylene) block copolymers(Pluronics) and lecithin. Preferred solubilizing aids are polyethyleneglycol, and Pluronics.

Bacteriostats useful in the preparation of radiopharmaceuticals and indiagnostic kits useful for the preparation of the radiopharmaceuticalsinclude but are not limited to benzyl alcohol, benzalkonium chloride,chlorbutanol, and methyl, propyl or butyl paraben.

A component in a diagnostic kit can also serve more than one function. Areducing agent can also serve as a stabilization aid, a buffer can alsoserve as a transfer ligand, a lyophilization aid can also serve as atransfer, ancillary or co-ligand and so forth.

The predetermined amounts of each component in the formulation aredetermined by a variety of considerations familiar to those skilled inthe art. These considerations are in some cases specific for thatcomponent and in other cases dependent on the amount of anothercomponent or the presence and amount of an optional component. Ingeneral, the minimal amount of each component is used that will give thedesired effect of the formulation. The desired effect of the formulationis that the practicing end user can synthesize the radiopharmaceuticaland have a high degree of certainty that the radiopharmaceutical can besafely injected into a patient and will provide diagnostic informationabout the disease state of that patient.

EXAMPLES Example 1

In a preferred embodiment of the present invention, oxidants of theinvention are added to a compound of Formula I, a ^(99m)Tc(V)-diaminedioxime complex that contains a 2-nitroimidazole substituent:

1. Preparation of a Complexing Ligand for the Compound of Formula I

The structure of the complexing ligand of Formula II is as follows:

This ligand, which complexes with ^(99m)Tc to form the compound ofFormula I, may be prepared as set forth below. Additionally, methods forthe preparation of various complexing ligands, including the Compound 1complexing ligand, are set forth in U.S. Pat. No. 5,608,110, thedisclosure of which is incorporated by reference herein in its entirety:

A. Preparation of2-[2-Hydroxy-2-(nitro-1H-imidazole-1-yl)ethyl]-1H-isoindole-1,3(2H)-dione.

To a solution of N-(2,3-epoxypropyl)phthalimide (commercially available,25.0 g, 0. 123 mol) in ethanol (200 mL) 2-nitroimidazole (commerciallyavailable, 14.5 g, 0.128 mol) and potassium carbonate (1.5 g) were addedand the reaction mixture was heated under reflux for about 6 hoursduring which time a light yellow solid formed. The reaction mixture wascooled and the yellow solid obtained was filtered and dried. m.p.213-14° C.

B. Preparation of a-(Aminomethyl)-2-nitro-1H-imidazole-1-ethanol.

To a suspension of2-[2-hydroxy-2-(nitro-1H-imidazol-1-yl)ethyl]-1H-isoindole-1,3(2H)-dionefrom Step A. (43.3 g, 0.37 mol) in methanol (400 mL), anhydroushydrazine (5.5 g, 0.172 mol) was added and the mixture was refluxed forabout 8 hours. A clear solution was obtained after 1 hour and lightyellow solid began to separate after 3 hours. The reaction mixture wascooled and the methanol was removed on a rotary evaporator.

C. Preparation ofa-[(t-Boc-amino)methyl]-2-nitro-1H-imidazole-1-ethanol.

The light yellow solid obtained from Step B was treated with sodiumcarbonate (31.8 g. 0.3 mol) in water (200 mL). Tetrahydrofuran [THF](800 mL) was added to this mixture and cooled to about 0° C. Di-t-butyldicarbonate (43.6 g, 0.2 mol) was added to the THF-water mixture, andstirred at about 0° C. for 1 hour and RT for 72 hours. THF-water wasremoved on a rotary evaporator and the residue was extracted with ethylacetate (3×150 mL). The ethyl acetate layer was washed with water, driedover sodium sulphate (Na₂SO₄) and evaporated on a rotary evaporator toyield the title compound as a yellow solid. The yellow solid obtainedwas triturated with ether (200 mL) and filtered. It was recrystallizedfrom hexane-ethyl acetate, m.p. 128-29° C.

D. Preparation ofN-[1-[(t-Boc-amino)methly]-2-(2-nitro-1H-imidazol-1-yl)ethoxy)phthalimide.

N-hydroxyphthalimide (18.0 g, 0.11 mol),a-[t-Boc-amino)methyl]-2-nitro-1H-imidazole-1-ethanol (28.6 g, 0.1mol)), and triphenylphosphine (28.85 g, 0.11 mol), were dissolved in THF(200 mL), and treated with diethyl azodicarboxylate (21.75 g, 0.125mol). The reaction mixture became dark red and the color disappearedafter a few minutes. A slight exothermic reaction was observed duringthe addition of diethyl azodicarboxylate. The reaction mixture wasstirred at room temperature for about 24 hours, and evaporated on arotary evaporator to dryness. The residue was dissolved in ether (300mL), and the solid that formed was filtered and silica gel (100 g) wasadded to the filtrate. The solvent was evaporated on a rotary evaporatorto afford a free flowing powder. The free flowing powder was loaded onto a silica gel column (76×560 mm. 1.5 Kg) and eluted first withhexane-ethyl acetate 7:3, followed by hexane-ethyl acetate 3:7.Fractions containing the product were collected and evaporated to givethe product as a white foam.

E. Preparation of1-[2-(Aminooxy)-3-t-Boc-amino)propyl]-2-nitro-1H-imidazole.

Anhydrous hydrazine (2.0 g, 0.062 mol) was added to a solution of2-[1-[(t-Boc-amino)methyl]-2-(2-nitro-1H-imidazol-1-yl)ethoxy]1H-isoindole-1,3(2H)-dione(24.0 g, 0.056 mol) in methylene chloride (150 mL) and the mixture wasstirred at room temperature for about 6 hours. A light yellow solid(Phthalyl hydrazide) began to form within 10 min. The solid, whichformed, was filtered and the filtrate was evaporated on a rotaryevaporator. The thick oil obtained was triturated with ether (200 mL)and the resultant precipitate was filtered and dried under vacuum.Yield: 15.8 g (94%). This was used in the next step without furtherpurification. A portion of the amine was recrystallized fromhexane-ethyl acetate. m.p. 95-96° C.

F. Preparation of 1-[3-Amino-2-(aminooxy)propyl-2-nitro-1H-imidazoledihydrochloride.

Methanolic HCl (30 mL) was added to a solution of1-[2-(aminooxy)-3-(t-Boc-amino)propyl]-2-nitro-1H-imidazole (15.6 g,0.052 mol) in methanol (15 mL), and the mixture was stirred at roomtemperature for about 1 hour. Ether (200 mL) was added to the methanolicsolution and the 1-[3-amino-2-(aminooxy)propyl]-2-nitro-1H-imidazoledihydrochloride, which formed, was filtered and dried under vacuum.Yield 12.9 g (91%). A portion of the hydrochloride was crystallized frommethanol/ether. m.p. 143-44° C. dec.

G. Preparation of 3-chloro-3-methyl-2-nitrosobutane.

In a 500-mL 3-necked flask fitted with a mechanical stirrer, a droppingfunnel and a thermometer was placed 2-methyl-2-butene (91.4 mL, 0.846mol) at RT and, with stirring, isoamyl nitrite (107.4 mL, 0.8 mol) wasintroduced. The mixture was then cooled to about −15° C. andconcentrated HCl (89.5 mL, 0.907 mol) was added dropwise over a periodof about 40 min maintaining the temperature at −10° C. to −5° C., givinga light blue slurry. The slurry was stirred at −10° C. to −5° C. for anadditional 30 min. The pasty mass was filtered and washed with cold −20°C. petroleum ether. The wet product was dissolved in petroleum ether(b.p. 30-60° C., 400 mL) and the solution was decanted to remove waterand dried (Na₂SO₄). The solution was filtered and cooled to −50° C. withoccasional stirring, and the white crystalline solid was collected byfiltration, washed with cold (−50° C.) petroleum ether and dried undervacuum at RT overnight. m.p. 72-74° C.

H. Preparation of the Compound I Complexing Ligand:[3,3,9,9-Tetramethyl-6[(2-nitro-1H-imidazol-1-yl)methyl]-5-oxa-4,8-diazaundecane-2,10-dionedioxine]

In a nitrogen-flushed, 500 mL round bottomed flask equipped with amagnetic stirrer were placed1-[3-Amino-2-(aminooxy)propyl]-2-nitro-1H-imidazole dihydrochiloride(12.74 g, 0.0465 mol). acetonitrile (150 mL), and N,N′-diisopropylethylaimine (32.4 g, 43.7 mL, 0.25 mol).3-Chloro-3-methyl-2-nitrosobutane (14.9 g, 0.11 mol) was added to thismixture and stirred at room temperature for 12 hours. (When the3-chloro-3-methyl-2-nitrosobutane was added, the reaction mixture becameslightly exothermic). Acetonitrile was removed on a rotary evaporatorand the thick oil obtained was basified with saturated potassiumcarbonate solution (25 g, in 25 mL of water). The light green oilobtained was extracted with ethyl acetate and dried over Na₂SO₄. Ethylacetate was removed on a rotary evaporator and the oil obtained wasdried under vacuum to afford a foamy solid. The foamy solid wasdissolved in acetonitrile (200 mL) and left at room temperature forabout 2 hours. The solid that formed was filtered and recrystallizedfrom acetonitrile. m.p. 170-171° C.

For the experiments set forth below, the complexing ligand was used inthe form of a freeze-dried formulation containing 2 mg of the complexingligand of Formula II.

2. Preparation of the Compound of Formula I without Oxidants of theInvention

The compound of Formula I was prepared in the absence of oxidants of theinvention using a freeze-dried formulation containing the complexingligand discussed above, and one of two different commercially availablekits for the preparation of ^(99m)Tc-DTPA (Techneplex-DTPA kit andDraximage-DTPA kit) as the stannous source. In the first preparation(Preparation 1), a freeze-dried formulation containing 2 mg of thecomplexing ligand of Formula II was dissolved in a sufficient amount of^(99m)TcO₄ ⁻ generator eluent to reach an activity of about 40 mCi. Tothis solution was added a sufficient amount of saline to bring thevolume to 2.0 mL, followed by 0.5 mL of the Techneplex-DTPA (17.5 μg ofSnCl₂) kit (reconstituted with 10 mL of saline).

In the second preparation (Preparation 2), a freeze dried formulationcontaining 2 mg of the complexing ligand of Formula II was dissolved ina sufficient amount of ^(99m)TcO₄ ⁻ generator eluent to reach anactivity of about 40 mCi. To this solution was added a sufficient amountof saline to bring the volume to 2.0 mL, followed by 0.5 mL of theDraximage-DTPA (17.5 μg of SnCl₂) kit (reconstituted with 10 mL ofsaline).

Aliquots of Preparations 1 and 2 were withdrawn after about six hoursand analyzed by HPLC. The compound was eluted using the followingconditions: isocratic elution, 45% CH₃CN/55% 0.1 M ammonium acetate pH4.0, flow rate about 1 mL/min, YMC Basic S5 4.6×250 mm column.

Paper chromatography was employed to determine the quantity ofradiocolloid present in each kit using Gelman solvent saturator padsdeveloped in 50:50 methanol:saline. In this system, the percentage ofactivity retained at the origin corresponds to the % of radiocolloid.

Using Preparation 1 of the compound of Formula I, RCP's of greater than90% at six hours were not obtained. The HPLC chromatogram shown in FIG.1 illustrates the composition of Preparation 1 (reconstituted from a kitusing Techneplex-DTPA as the stannous source at six hours postreconstitution). The side products formed are mostly hydrophilic specieswith a shorter retention time (2.8, 3.6 and 4 min) than the compound ofFormula I, which elutes at 5.7 min. The peak eluting at 2.8 min. wasidentified as TcDTPA, the peak at 3.6 min. as TcO₄ ⁻, while the peak at4 min. may be a reduced form of the compound of Formula 1. Anunidentified lipophilic peak eluting at 6.9 min that accounts for up to3% of the radioactivity is also present.

The HPLC chromatogram shown in FIG. 2 illustrates that when a differentcommercially available Sn-DTPA source, Draximage-DTPA, was used toprepare the compound of Formula I (Preparation 2), the RCP increased toabout 90% at six hours but the unidentified lipophilic peak was stillpresent.

The only difference between the Techneplex-DTPA and the Draximage-DTPAkit formulations is the presence of p-aminobenzoic acid (PABA) in thelatter one. PABA is a known radical scavenger (Hu, Miao Lin; ChenLing-Chun; Sano, Miitsuaki: Para-aminobenzoic acid scavenges reactiveoxygen species and protects DNA against UV and free radical damage. J.Nutr. Biochem. 1995, 6(9) 504-8) and appears to be able to neutralizethe radical anion NO₂, the first step in the reduction cascade of thenitro group.

It is believed that the excess of stannous present after the reductionof the pertechnetate, together with the radicals generated byradiolysis, were responsible for the reduction of the nitroimidazolemoiety on the compound of Formula I, leading to the formation of bothhydrophilic and lipophilic impurities over time.

3. Preparation of the Compound of Formula I with Oxidants of theInvention

To inhibit this degradation, the compound of Formula I was formulatedwith a number of different oxidants. Except as indicated in Table 1, theoxidants were added before complexation of ^(99m)Tc with the complexingligand of Formula II. Thus, sodium hypochlorite and Benzoquinone, CASRegistry No. 106-51-4, were added before complexation in someformulations and after complexation in other formulations. However, theremaining oxidants tested (Coenzyme Q0, iodine, KMnO₄, CuCl₂, CuBr andFeCl₃) were all added prior to complexation.

The procedure for addition of the oxidants before the complexation isillustrated with Benzoquinone, CAS Registry No. 106-51-4:

A freeze-dried formulation containing 2 mg of the complexing ligand ofFormula II was dissolved in a sufficient amount of ^(99m)TcO₄ ⁻generator eluent to yield an activity of about 40 mCi. To this solutionwas added in the following order: 135 μL of a 1.15 mM solution ofbenzoquinone, sufficient saline to bring the volume to 2.0 mL, and 0.5mL of a Draximage-DTPA (17.5 μg of SnCl₂) kit (reconstituted with 10 mLof saline).

The procedure for addition of the oxidants after complexation is alsoillustrated with benzoquinone:

A freeze-dried formulation containing 2 mg of the complexing ligand ofFormula II was dissolved in a sufficient amount of ^(99m)TcO₄ ⁻generator eluent to reach an activity of about 40 mCi. To this solutionwas added sufficient saline to bring the volume to 2.0 mL, followed by0.5 ml of the Draximage-DTPA (17.5 μg of SnCl₂) kit (reconstituted with10 mL of saline). Fifteen minutes later, 135 μL of a 1.15 mM solution ofbenzoquinone was added.

4. Testing Formulations of the Compound of Formula I with Oxidants ofthe Invention

Formulations of the compound of Formula I containing oxidants of theinvention were assessed for RCP (radiochemical purity) by HPLC at 15minutes and 6 hours using the procedure described above. Many oxidants,organic and inorganic, with potentials ranging from 1.358 to 0.341 volts(relative to the standard hydrogen electrode) were tested. Althoughthese oxidants were able to oxidize Sn²⁺, many of them still allowedcomplex formation when added prior to stannous addition. The resultsobtained with the various formulations of Compound I and differentoxidants are summarized in Table 1 below.

As shown in Table 1, strong oxidants, such as sodium hypochlorite, mustbe added after complex formation. Table 1 illustrates that thc RCP offormulations of the compound of Formula I containing oxidants was wellover 90% at six hours and the lipophilic impurity eluting at 6.9 min wascompletely eliminated. TABLE 1 Effect of oxidants on RadiochemicalPurity (RCP) of Compound 1 Ratio of Amount of 15 min. 6 hr. OxidantSn:Oxidant Oxidant RCP RCP Lipophilic peak 6 hr. Benzoquinone 1:1 8.4 μg96.2 Not detectable Benzoquinone 1:2 16.8 μg 96.2 Not detectableBenzoquinone 1:2 16.8 μg 98.2 96 Not detectable Benzoquinone 1:2 16.8 μg98 95.7 Not detectable Benzoquinone 1:1 8.4 μg 96.5 96.5 Not detectableBenzoquinone 1:0.7 5.9 μg 97.9 96.2 Not detectable Benzoquinone 1:1.411.8 μg 98 96.3 Not detectable Benzoquinone 1:3.5 29.4 μg 97.8 95.8 Notdetectable Benzoquinone 1:5 42 μg 97.3 95 Not detectable Benzoquinoneafter 1:10 84 μg 97.3 94.2 Not detectable addition of Draximage DTPABenzoquinone after 1:15 126 μg 96.7 93.5 Not detectable addition ofDraximage DTPA Coenzyme Q0 1:25 353 μg 95.7 94.7 Not detectable CoenzymeQ0 1:25 353 μg 93 91.2 Not detectable Coenzyme Q0 1:25 353 μg 95.9 93.1Not detectable Tetrahydroxy 1:2 26.7 μg 95.6 87.3 1.1 benzoquinoneIodine 1:1.4 27 μg 97.9 95.3 Not detectable Iodine 3.4 67 μg 96.5 93.3Not detectable KMnO₄ 1:0.39 7 μg 93.3 89 1.9 KMnO₄ 1:1 18 μg 97.6 92.91.6 KMnO₄ 1:2 37 μg 97.6 92.2 2.3 KMnO₄ 1:3 55 μg 97.4 91.2 3 Sodiumhypochlorite 1:2.4 12 μg of Cl₂ 10 Not detectable Sodium hypochlorite1:1 5 μg of Cl₂ 49.5 Not detectable Sodium hypochlorite 1:1 5 μg of Cl₂97 92.6 Not detectable after addition of DraximageDTPA Sodiumhypochlorite 1:1 5 μg of Cl₂ 96.8 93.4 Not detectable after addition ofDraximageDTPA Sodium hypochlorite 1:2 10 μg of Cl₂ 97.4 93.4 Notdetectable after addition of DraximageDTPA Sodium hypochlorite 1:5 25 μgof Cl₂ 97.2 93.6 Not detectable after adddition of DraximageDTPA CuCl₂1:1 13 μg 97.3 93.9 1.5 CuCl₂ 1:2 26 μg 4.3 CuBr 1:2 22 μg 94.8 92.5 1CuBr 1:3 33 μg 98 94 0.8 FeCl₃ 1:2 84 μg 95.5 91.1 1.2

The percentage of ^(99m)Tc-radiocolloid, which is not detectable byHPLC, was determined by paper chromatography, as described above. Thepercentages were in the normal average (0.5-1.0%) for all thereconstituted kits.

FIG. 3 is the HPLC chromatogram of a formulation of the compound ofFormula 1 containing benzoquinone, CAS Registry No. 106-51-4, at 6 hourspost reconstitution. This figure illustrates the improvement achievedwith the use of benzoquinone: the lipophilic peak is not present and theunidentified hydrophilic impurities are below 1%.

Example 2

The next step of this study was to freeze dry different formulations ofthe compound of Formula I containing coenzyme Q₀, a preferred oxidant ofthe invention, and one of several bulking agents. The introduction of abulking agent is necessary to form a visible and stable pellet at thebottom of the vial.

Coenzyme Q₀ was selected for use in this experiment because it is moresuitable for a freeze drying process than either iodine, which caneasily sublime in the process, or sodium hypochlorite, which wasrejected because, being a very strong oxidizer, it has to be introducedafter complex formation and thus requires a three vial formulation.

Four formulations containing 4 mg of the complexing ligand of FormulaII. 0.7 mg of coenzyme Q₀ and 10 mg of one of several bulking agentswere prepared and freeze dried. Specifically, the complexing ligand ofFormula II was dissolved in 90 ml of a pH 2.1 HCl solution and the pHwas adjusted to 8.2 using 0.1. N NaOH. 35.4 mg of coenzyme Q₀ (dissolvedin 5 mL of water) was added and the volume was adjusted to 100 mL. Thisbulk solution was divided in four 25 mL aliquots. 250 mg of the bulkingagent was added to each aliquot and the pH was adjusted to 8.2 using0.001 N NaOH. These solutions were filtered and 2 mL of each formulationwas dispensed in vials for the freeze drying process. The freeze-driedformulations were reconstituted with 40 mCi of ^(99m)TcO₄ ⁻ usingDraximage-DTPA as the stannous source, as described in Example 1. Theformulations were analyzed by HPLC at 15 minutes, 2 hours, 4 hours and 6hours using the conditions described. The results are suminarized inTable 2. TABLE 2 RCP Values For Freeze-dried Kits Lipophilic Bulkingagent 15 min. 2 hr. 4 hr. 6 hr. peak 6 hr. 20 mg of Sucrose 97 96.7 95.394.6 Not detectable 20 mg of Dextran 96.1 94.7 94 93 Not detectable 20mg Hydroxypropyl-γ- 96.8 95.8 94.9 94.2 Not detectable cyclodextrin 20mg Maltose 96.8 94.8 94.8 94.2 Not detectable

The percentages of radiocolloid were in the normal average (0.5-1.0%)for all the reconstituted kits. All formulations tested had an RCPgreater than 90% at six hours after reconstitution when reconstitutedwith 40 mCi of ^(99m)Tc.

As previously stated, detailed embodiments of the present invention aredisclosed herein; however, it is to be understood that the disclosedembodiments are merely exemplary of the invention that may be embodiedin various forms. It will be appreciated that many modifications andother variations that will be appreciated by those skilled in the artare within the intended scope of this invention as claimed below withoutdeparting from the teachings, spirit and intended scope of theinvention.

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each independent publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

1. A kit for preparing a radiopharmaceutical, the kit comprising apredetermined quantity of a complexing ligand and a predeterminedquantity of an oxidant. wherein the radiopharmaceutical has aradiochemical purity of greater than 90% at about six hours afterreconstitution.
 2. The kit of claim 1, wherein the oxidant has thefollowing structure:

where R₁, R₂, R₃, and R₄ are independently selected from hydrogen,hydroxyl, halogen, lower alkyl, alkoxy, aryl, heteroaryl, NO₂ and

where n is an integer from 0 to 12; or where R₁ and R₂ taken togetherform a ring and R₃ and R₄ are as defined above.
 3. The kit of claim 1,wherein the oxidant is benzoquinone.
 4. The kit of claim 1, wherein theoxidant has the following structure:

where n is an integer from 0 to
 12. 5. The kit of claim 4, wherein theoxidant is coenzyme Q₀.
 6. The kit of claim 1, wherein the ligand andthe oxidant are in one vial.
 7. The kit of claim 1, wherein theradiochemical purity is greater than about 92% at about six hours afterreconstitution.
 8. The kit of claim 1, wherein the radiochemical purityis greater than about 95% at about six hours after reconstitution. 9.The kit of claim 1, wherein the complexing ligand comprises a compoundof Formula II:


10. The kit of claim 1, further comprising a reducing agent.
 11. The kitof claim 10, wherein wherein the reducing agent is selected fromstannous chloride, stannous pyrophosphate, stannous fluoride, stannoustartrate, stannous glucoheptonate, stannous DTPA, a borohydride salt,sodium dithionite, a Cu(I) salt, and a formamidine sulphinic acid. 12.The kit of claim 11, wherein the reducing agent is a stannous compound.13. The kit of claim 12, wherein the stannous and the oxidant arepresent in a ratio from about 1:0.39 to about 1:25.
 14. The kit of claim1, wherein the radiopharmaceutical comprises a radionuclide selectedfrom ^(99m)Tc, ⁵¹Cr, ⁶⁷Cu, ⁹⁷Ru, ¹⁸⁸Re, ¹⁸⁶Re, and ¹⁹⁹Au.
 15. The kit ofclaim 1, further comprising a transfer ligand, a bulking agent, abuffer, a stabilization aid, a solubilization aid or a bacteriostat. 16.The kit of claim 15, wherein the bulking agent is selected from maltose,sucrose, and hydroxypropyl-γ-cyclodextrin.
 17. A kit for the preparationof a radiopiharmaceutical, the kit comprising a lyophilized compositioncomprising a predetermined quantity of a complexing ligand and apredetermined quantity of an oxidant, wherein the oxidant has thefollowing structure:

where R₁, R₂, R₃, and R₄ are independently selected from hydrogen,hydroxyl, halogen, lower alkyl, alkoxy, aryl, heteroaryl, NO₂ and

where n is an integer from 0 to 12: or where R₁ and R₂ taken togetherform a ring and R₃ and R₄ are as defined above.
 18. The kit of claim 17,wherein the radiopharmaceutical has a radiochemical purity of greaterthan 90% at about six hours after reconstitution.
 19. The kit of claim17, wherein the radiochemical purity is greater than about 95% at aboutsix hours after reconstitution.
 20. The kit of claim 17, wherein theoxidant is benzoquinone.
 21. The kit of claim 17, wherein the ligand andoxidant are in one vial.
 22. The kit of claim 17, wherein the oxidanthas the following structure:

where n is an integer from 0 to
 12. 23. The kit of claim 22, wherein theoxidant is coenzyme Q₀.
 24. The kit of claim 22, wherein theradiochemical purity is greater than about 92% at about six hours afterreconstitution.
 25. The kit of claim 22, further comprising a reducingagent.
 26. The kit of claim 25, wherein the reducing agent is selectedfrom stannous chloride, stannous pyrophosphate, stannous fluoride,stannous tartrate, stannous glucoheptonate, stannous DTPA, a borohydridesalt, sodium dithionite, a Cu(I) salt, and a formamidine sulphinic acid.27. The kit of claim 26, wherein the reducing agent is a stannouscompound.
 28. The kit of claim 27, wherein the stannous and the oxidantare present in a ratio from about 1:0.39 to about 1:25.
 29. The kit ofclaim 22, wherein the radiopharmaceutical comprises a radionuclideselected from ^(99m)Tc, ⁵¹Cr, ⁶⁷Cu, ⁹⁷Ru, ¹⁸⁸Re, ¹⁸⁶Re, and ¹⁹⁹Au. 30.The kit of claim 22, further comprising a transfer ligand, a bulkingagent, a buffer, a stabilization aid, a solubilization aid or abacteriostat.
 31. The kit of claim 30, wherein the bulking agent isselected from maltose, sucrose, and hydroxypropyl-γ-cyclodextrin.
 32. Akit for the preparation of a radiopharmaceutical, the kit comprising apredetermined quantity of a complexing ligand of Formula II:

a predetermined quantity of coenzyme Q₀, and a bulking agent selectedfrom maltose, sucrose, and hydroxypropyl-γ-cyclodextrin.
 33. The kit ofclaim 32, wherein the radiopharmaceutical has a radiochemical purity ofgreater than 90% at about six hours after reconstitution.
 34. The kit ofclaim 32, wherein the radiochemical purity is greater than about 92% atabout six hours after reconstitution.
 35. The kit of claim 32, whereinthe radiochemical purity is greater than about 95% at about six hoursafter reconstitution.
 36. The kit of claim 32, wherein the ligand andthe coenzyme Q₀ are in one vial.
 37. The kit of claim 32, furthercomprising a reducing agent.
 38. The kit of claim 37, wherein whereinthe reducinig agent is selected from stannous chloride, stannouspyrophosphate, stannous fluoride, stannous tartrate, stannousglucoheptonate, stannous DTPA, a borohydride salt, sodium dithionite, aCu(I) salt, and a formamidine sulphinic acid.
 39. The kit of claim 38,wherein the reducing agent is a stannous compound.
 40. The kit of claim39, wherein the stannous and the oxidant are present in a ratio fromabout 1:0.39 to about 1:25.
 41. The kit of claim 32, wherein theradiopharmaceutical comprises a radionuclide selected from ^(99m)Tc,⁵¹Cr, ⁶⁷CU, ⁹⁷Ru, ¹⁸⁸Re, ¹⁸⁶Re, and ¹⁹⁹Au.
 42. The kit of claim 32,further comprising a transfer ligand, a bulking agent, a buffer, astabilization aid, a solubilization aid or a bacteriostat.
 43. The kitof claim 42, wherein the bulking agent is selected from maltose,sucrose, and hydroxypropyl-γ-cyclodextrin.
 44. A pharmaceuticalcomposition comprisinig a radiopharmaceutical and an oxidant, whereinthe radiopharmaceutical has a radiochemical purity of greater than 90%at about six hours after reconstitution.
 45. The composition of claim44, wherein the oxidant has the following structure:

where R₁, R₂, R₃, and R₄ are independently selected from hydrogen,hydroxyl, halogen, lower alkyl, alkoxy, aryl, heteroaryl, NO₂ and

where n is an integer from 0 to 12, or where R₁ and R₂ taken togetherform a ring and R₃ and R₄ are as defined above.
 46. The composition ofclaim 45, wherein the oxidant is benzoquinone.
 47. The composition ofclaim 45, wherein the oxidant has the following structure:

where n is an integer from 0 to
 12. 48. The composition of claim 47,wherein the oxidant is coenzyme Q₀.
 49. The composition of claim 48,wherein the radiopharmnceutical comprises a compound of formula I:


50. The composition of claim 49, further comprising a transfer ligand, abulking agent, a buffer, a stabilization aid, a solubilization aid or abacteriostat.
 51. The composition of claim 50, wherein the bulking agentis selected from maltose, sucrose, and hydroxypropyl-γ-cyclodextrin. 52.The composition of claim 44, wherein the radiopharmaceutical comprises aradionuclide selected from ^(99m)Tc, ⁵¹Cr, ⁶⁷CU, ⁹⁷Ru, ¹⁸⁸Re, ¹⁸⁶Re, and¹⁹⁹Au.
 53. The composition of claim 44, wherein the composition has aradiochemical purity of greater than about 92% at about six hours afterreconstitution.
 54. The composition of claim 44, wherein the compositionhas a radiochemical purity of greater than about 94% at about six hoursafter reconstitution.
 55. The composition of claim 44, wherein thecomposition has a radiochemical purity of greater than about 96% atabout six hours after reconstitution.
 56. A method of making aradiopharmaceutical composition, comprising the steps of: a) contactinga complexing ligand with a radionuclide to form a complex; and b)contacting the complexing ligand with an oxidant, wherein theradiopharmaceutical composition has a radiochemical purity of greaterthan about 90% at about six hours after reconstitution.
 57. The methodof claim 56, further comprising the step of contacting a reducing agentwith a radionuclide source to generate the radionuclide.
 58. The methodof claim 56, further comprising the step of reducing a radionuclidesource with a transfer ligand to generate the radionuclide.
 59. Themethod of claim 56, wherein step b) is performed prior to step a). 60.The method of claim 56, wherein step b) is performed simultaneously withstep a).
 61. The method of claim 56, wherein the oxidant has thefollowing structure:

where R₁, R₂, R₃, and R₄ are independently selected from hydrogen,hydroxyl, halogen, lower alkyl, alkoxy, aryl, heteroaryl, NO₂ and

where n is an integer from 0 to 12; or where R₁ and R₂ taken togetherform a ring and R₃ and R₄ are as defined above.
 62. The method of claim61, wherein the oxidant is benzoquinone.
 63. The method of claim 61,wherein the oxidant has the following structure:

where n is an integer from 0 to
 12. 64. The method of claim 63, whereinthe oxidant is coenzyme Q₀.
 65. The method of claim 56, wherein thecomplexing ligand comprises a compound of Formula II:


66. The method of claim 65, wherein the radiopharmaceutical comprises acompound of Formula I:


67. The method of claim 56, wherein the radionuclide is selected from⁹⁹Tc, ⁵¹Cr, ⁶⁷Cu, ⁹⁷Ru, ¹⁸⁸Re, ¹⁸⁶Re, and ¹⁹⁰Au.
 68. The method of claim56, wherein the radiopharmaceutical composition has a radiochemicalpurity of greater than about 92% approximately six hours after thecomplex is formed.
 69. The method of claim 56, wherein theradiopharmaceutical composition has a radiochemical purity of greaterthan about 94% approximately six hours after the complex is formed. 70.The method of claim 56, wherein the radiopharmaceutical composition hasa radiochemical purity of greater than about 96% approximately six hoursafter the complex is formed.
 71. A radiopharmaceutical made by themethod of claim 56.